In blood gas analysis, it is important that air or other gaseous materials not be allowed to contaminate the blood as these contaminates distort the results of the gas analysis. Accordingly, prior art syringes adapted to withdraw blood samples from donors are normally preconditoned by the addition of a heparin solution to fill the void or dead space in the syringe and needle and to purge the syringe and needle of air or other gaseous materials and to provide an anticoagulant for the blood. The heparin solution, however, is typically very dilute with the heparin concentration being approximately 1000 units per milliliter and the diluent being made up of alcohol, water, and other materials which can also distort the gas analysis of the blood.
Therefore, it is desirable in taking blook samples for gas analysis to isolate the blood from extraneous gaseous materials and from the diluent of the heparin solution while leaving the heparin itself to prevent coagulation of the blood.
Accordingly, it is an object of the present invention to provide a new and improved syringe for taking blood samples which prevents contamination by extraneous gases or the diluent of a heparin solution.
It is another object of the present invention to provide a syringe for taking blood from a donor wherein the syringe has a vent opening through which air and other gaseous materials can be removed from the interior chamber of the syringe so that blood admitted into the syringe is not contaminated thereby.
It is still another object of the present invention to provide a syringe having a coating of a dry heparin material in the interior thereof to prevent the coagulation of blood drawn into the syringe and vent means for removing air from the interior chamber of the syringe so that the air does not contaminate the blood admitted to the syringe.